A lithium ion battery is a member of a family of rechargeable battery types in which lithium ions move from the anode to the cathode during discharge and back when charging. Lithium-ion batteries are common in many consumer electronics as they are one of the most popular types of rechargeable batteries for portable electronics.
The growing popularity of incorporating lithium ion batteries into an increasing range of products is likely based, at least in part, on the fact that lithium ion batteries have one of the best energy densities, no (or minimal) memory effect, and only a slow loss of charge when not in use. By utilizing lithium, which has a small specific gravity and high electrochemical reactivity, lithium ion batteries can store two to three times the energy of other rechargeable batteries such as Ni—Cd or Ni-MH batteries. In addition to consumer products, lithium ion batteries are also growing in popularity in the automotive industry and aerospace applications as the relatively light weight lithium ion batteries can provide the same or similar voltage as traditional lead-acid batteries without the “extra” weight associated with lead-acid batteries.
Despite the positive attributes of lithium ion batteries, there have been concerns associated with their use. The undesirable heating and fire caused by lithium-ion batteries has been referred to as “thermal runaway”. In such cases, for example, a compromised separator in an individual cell can result in an internal short causing severe internal heating of the cell until the compromised cell vents hot gas and internal (flammable) cell materials. Unfortunately, the severe heating and/or venting of materials from a compromised cell can often times provide enough heat to an adjoining cell to cause the adjoining cell to also begin venting hot gas and internal (flammable) cell materials.
Some causes for thermal runaway include internal short circuits (as referenced earlier), overcharging of the batteries, or the combination of both. Overcharging leads to the heating of the cathode side of the cell. In charging a lithium ion battery, lithium ions are pulled out of the cathode material and inserted into the anode material. However, in this process, the cathode material from which lithium ions are extracted from becomes unstable in terms of crystal structure. In usual circumstances, lithium ion batteries are controlled so that the amounts of lithium ions extracted from the cathode do not go beyond a certain level. In cases of overcharging, however, an excessive level of lithium ions is pulled out of the cathode material and leads to the collapse of the crystal structure of the cathode material resulting in the development of an exothermic reaction. The heat generated from such a reaction can initiate the successive venting of adjoining cells (e.g., a thermal runaway).
Current approaches for addressing thermal runaway generally rely on the use of gel packs including phase change materials. Such approaches rely on inserting the gel packs at physical interfaces between groups of one or more lithium-containing battery cells. For example, the gel packs containing the phase change material can be wrapped around each battery cell to absorb heat generated from a failed battery cell. Generally, the gel packs utilize a hydrated hydrogel as the phase change material in which the water stored in the hydrogel undergoes vaporization upon overheating of a battery cell. That is, the water in the hydrogel vaporizes to enable absorption of a large quantity of heat from the overheating cell to mitigate the possibility of a thermal runaway of a lithium-containing battery. The use of phase change materials in gel packs, however, suffers from many shortcomings. For example, failure of one battery cell nonetheless releases lithium-containing electrolyte gas from the cell exposing lithium metal to moisture in the surrounding air, which generates flammable hydrogen gas. Additionally, thermal runaway may still occur if a gel pack covers an insufficient surface area of a cell. That is, gel packs are only able to provide partial direct surface coverage of the individual cells which can severely limit such a system's ability to resolve temperature spikes in a battery cell. The surface area coverage shortcomings associated with the use of gel packs limits the effectiveness of such an approach to addressing thermal runaway.
For at least these reasons, there remains a need for methods of preventing and/or suppressing thermal runaway in lithium-containing batteries and containers housing lithium-containing batteries.